I recently improved the performance of my 2004 CPI Hussar by removing the front section of the exhaust header pipe, and bringing it into a muffler shop to have an identical pipe made in the diameter of the rear section of pipe. This cost me $60. I then painted it black with heat-proof paint before installing. It looks totally stock. Next, I took the cover off the transmission to get access to the variator. You will need an impact wrench to take the nut off the variator shaft, but after that, it is simple. Once you have the variator off, you will notice a washer located between the two halfs of the pulley. It looks very much like a spacer on an inline skate axle/bearing assembly. This is a restriction! That little washer does not let the two halves come completely together, which prevents the scooter from going into its highest gearing. Removing it took about 10 minutes of my time, including reassembly. The result of the above is that the bike now easily accelerates to 60kph, and can surpass 70kph on a downhill run. If you want more performance without spending much money, the next thing to do is go to a bigger mainjet in the carburator, and to increase air flow thru the airbox. I warn you that the mainjet has to be increased first, as the bike is carburated in such a way that it will not run if you increase the airflow, as it sucks air thru a straw-sized hole in its stock form, and is carburated accordingly. If you increase airflow before changing the mainjet, it will run so lean that it will only idle. It is tuned stock to suck hard thru the small airbox opening, which actually makes it run in a consstant "choked" state. To successfully do this, it has a very small mainjet, and I would recommend starting by going to a .8mm. As in all 2-strokes, better a tad rich rather than lean. Hope this helps.